Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          468        178 
1992          743        301 
1993         1308        487 
1994         1678        616 
1995         3048       1064 
1996         2980       1053 
1997         1860        642 
1998        21677       9216 
1999        13481       5173 
2000        38615      15964 
2001        39435      15317 
2002        33278      14631 
2003        57753      24029 
2004        46309      17767 
2005        81400      25058 
2006       105068      33722 
2007       191835      59294 
2008       112312      32160 
2009        93135      26251 
2010       143977      38735 
2011       157957      43815 
2012       149310      41369 
2013       221100      62989 
2014       565348     144040 
2015       798432     210136 
2016       659219     171312 
2017       554756     150158 
2018       351621      98777 
2019       863745     210848 
2020       617116     157046 
2021       830211     197130 
2022       620010     177470 
2023       558982     159907 
2024       618122     178121 
2025       217977      62352